1. Field of the Invention
The present invention relates to an imaging apparatus that includes a solid-state imaging device and a printed-circuit board connected to the solid-state imaging device and that has the printed-circuit board electrically connected to a composite cable. More particularly, this invention is concerned with a structure of connecting the printed-circuit board to the cables of the composite cable.
2. Description of the Related Art
In recent years, endoscopes having an elongated insertion unit thereof inserted in a body cavity in order to observe an organ in the body cavity or having if necessary a treatment appliance inserted in a treatment appliance channel in order to conduct various curative procedures or treatments have been adopted widely.
The endoscopes adopted as mentioned above include an electronic endoscope (hereinafter abbreviated to an endoscope) in which: a solid-state imaging device such as a CCD is placed in the distal part of the insertion unit thereof; an optical image formed on the CCD via an objective optical system is photoelectrically transferred into an electric signal; the electric signal is transmitted to a signal processing unit over a signal cable and converted into a video signal; and the video signal is visualized in a monitor screen.
The CCD in the endoscope and the signal processing unit that is an external unit are linked generally by a composite cable made by bundling up a plurality of cables in order to supply driving power to the CCD, transmit a video signal, or transmit a clock. For the composite cable, a coaxial cable is used as a signal line as a countermeasure against noises, and a plain cable is used as a power line.
When the cables contained in a composite cable are connected to a CCD or a printed-circuit board such as a hybrid IC (hereinafter an HIC) or flexible printed-circuit board (FPC) which is electrically connected to the CCD, the plurality of cables are separated from one another and then connected to electrodes formed on the printed-circuit board.
However, when cables contained in a composite cable are coaxial cables, the work of removing the armors of the coaxial cables is needed so that the conductors and shields of the coaxial cables can be soldered to different places. The work of removing the armors of the coaxial cables and connecting the coaxial cables is laborious. Moreover, a certain length of connection is needed to connect the coaxial cables to a printed-circuit board. This becomes an obstruct in reducing the diameter and length of an imaging apparatus.
An imaging apparatus employed in an endoscope is located in the distal part of an insertion unit of the endoscope. When the imaging apparatus is made shorter, the length of a rigid section of the distal part of the endoscope can be reduced, and inserting efficiency can be improved. The reduction in diameter and length of the imaging apparatus has been demanded even in an effort to improve the efficiency in inserting an endoscope.
In order to shorten an imaging apparatus, Japanese Patent Laid-Open No. 5-161602 has disclosed a structure in which: a printed-circuit board having ground electrodes formed on one side thereof and signal electrodes formed on the other side thereof, and having through holes for linking the electrodes is placed vertically; cables are passed through the through holes; and signal conductors and shields of the cables are connected to the signal electrodes and ground electrodes on the printed-circuit board. Using the art disclosed in the unexamined publication, cables can be connected to a printed-circuit board using only the thickness of the printed-circuit board. Shortening an imaging apparatus can be achieved.
However, when the art disclosed in the Japanese Patent Laid-Open No. 5-161602 is used to connect a composite cable to a printed-circuit board, the work of separating the cables of the composite cable from one another and the work of passing the respective cables through a through hole of the printed-circuit board and connecting them to electrodes are still necessary. For reinforcing the respective cables connected to the printed-circuit board, these mutually-separated cables are fixed all at once using an adhesive or the like. As a result, a rigid area made from the adhesive is formed on the rear side of the printed-circuit board. This makes it difficult to greatly shorten an imaging apparatus.